“New Year’s Day” is the final track on Reputation, a soft, keyboard-heavy outlier after a suite of crushing pop songs. On The Tonight Show, Swift played the piano while an acoustic guitarist provided barely perceptible accompaniment and four backing vocalists added occasional harmony. “Please don’t ever become a stranger whose laugh I could recognize anywhere,” Swift sang.

Swift’s performance coincided with Fallon’s return to The Tonight Show after the death of his mother earlier this month. “[Swift] was not scheduled to do our show today,” The Tonight Show writer Mike DiCenzo explained on Twitter. “But we wanted something special for this first show back, so we asked her on a complete whim, since she had been in town doing SNL. She said yes with zero hesitation.” “Whatever you think of Taylor, she did something beautiful for Jimmy and our show today, and we’re forever grateful,” he added.

Swift released Reputation last Friday; according to Nielsen Soundscan, the album sold over 900,000 copies in three days, already the largest opening week of any album in 2017. (Reputation is currently not available on streaming services.) Swift informed her fans that buying extra copies of the new record will better position them to buy tickets for her upcoming tour. She’ll hit the road in support of Reputation beginning next May.